4 valve head/cam kit
 

My entire 911 cost less than those heads.

Anyone had these heads on a dyno? Previous kits were marketed, but always had issues.

Somebody's had them on the road if that helps.

https://m.youtube.com/watch?v=AndH7Xm3ds0

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An incredible piece of engineering, regardless.

I watched the video when it made rounds recently. Very impressive, and certainly is cool. I think the Tuthill guys might have even commented on the hp figure at some point that they had hoped for more. The car in the video is street legal, so who knows which tradeoffs have been made in the name of tractability for street driving. Would be interesting to see a race version to see what's possible. I wouldn't been shocked to see a killer "traditional" 3.0L make the same hp.

Either way, incredible bit of engineering as Neil said.

...did not know the Tuthill motor had these heads.

Though the max flow numbers are basically the same as Xtreme heads, the ramp up is a lot quicker with knee around 6-7mm. pulled the below off Swindon website.

Continues to amaze me the amount of on going development on these motors.

http://forums.pelicanparts.com/uploa...1696871729.jpg

I noticed the flow numbers, too. The two valve heads can be ported to flow as much as those 4 valve heads on the intake, but it takes some work. The 4 valve exhausts outflow the ported 2 valve heads by quite a bit though. And yes, I've ported quite a few heads and still have a flow bench at home, so I kinda know what I'm talking about.

The tiny little springs, retainers and the rest of the valvetrain likely contribute to the high rev capability more than anything else.

Only the dyno knows.....

The Xtreme heads of my race engine flow more air both intake and exhaust than those heads. But, nothing can be done with 2 valve heads to reduce the mass of the individual valves, springs, and retainers...

One would have the think there's a lot of potential to unlock with 12k RPM ...

Same thing I said on the other site. My experience with synchronized manual transmissions tells me there would be some additional modifications required to get these 30 year old transmissions to shift at an RPM they weren't designed for - even at 9k...I cant imagine 12k.

I think I would prefer a boosted alternative with a moderate redline and save the $30.000 thats left for other stuff.
Tuthills car is a 3.1 liter with a claimed 350 hp. Not super impressive with a 4 valve head that revs to the moon.

I would have expected that these heads would have 500+ potential, NA.

I'd have to agree on the hp. Hard to say what Tuthill left on the table as a tradeoff for road use. Have to imagine there's more to be had.

Interesting point on the trans. I don't normally think of transmissions as being sensitive to RPM like engines, but who knows. Certainly additional cooling would make sense + whatever one would normally do to accommodate anticipated power levels.

Camshafts must be a huge compromise if it only makes 350 HP from 3.1L and spins to 12k rpm.

6,000 vs 12,000 RPM
 

We have seen the four valve head and the engine that it is installed on. OK, 12k! Given the lower end in some configuration can handle 12k, what is the limitation on my 1983 3.0L engine. Is it the rotating mass, or the cam train, or does it just run out of air?

I am assuming that these numbers are at 28 inches of vacuum on the flow bench?

$30,000 and the heads are NOT ported? WTF?? I guess I won't be a customer...

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the heads are good for 12k, but the rest of the drivetrain wont be. without throwing 100k+ on it...

very nice piece of engineering though.

I am baffled by the cynicism displayed here. Someone comes out with "something" whether its good or bad should be commended for doing something.

One post reads, "the ports are not ported therefore I will not be a buyer". You read below his/her post of what car they own and I have to ask, would that person ever buy a set of these heads even if the heads were ported? Maybe the heads are worth more than their car is?

Some posts suggest that the heads do not flow enough, as other head do. Maybe they flow what they wanted them to flow. We don't know what the specifications called out for.

We develop parts for these engines along with many other companies. If it wasn't for those that do, most here would be building Subaru engines for their cars.

Maybe there have been some issues. Who hasn't had issues. I for one can claim a pile of disasters I cannot even look over. But that doesn't stop me and others from having the passion and drive to continue. You do find more answers in your failures than your successes.

It just amuses me when I read comments, like above. They would mean a lot more if those that made them, were known in the business for producing and offering, something, other than cynical posts.